I've never had a fruit fly make it through a wet airlock in a carboy. With buckets the airlock doesn't matter, they can get through the seals (or their larvae can).

I can't be certain, but I think it may have happened when the yeast popped the top on the 3 piece airlock during a vigorous ferment phase. Not sure how long it was exposed before I found it, but apparently long enough . .

I know it is hard to tell from the picture, but it isn't fuzzy like mold, it was more like a plasticine film that had some bubbles in it. It didn't smell like vinegar, just like dark beer.

Acetobactor likes to form a plastic like film over the surface of the beer. The picture doesn't show that. However, if it the beer is taking on an acetic aroma and has a vinegar-like flavor then it is an acetobactor infection for sure.

It takes a while for the beer to start smelling like vinegar though. I've had acetobacter infections that actually didn't taste terrible. No sourness noted. Not something I could ever enjoy, but not much sourness going on either. It takes along time for acetobacter to fully convert the alcohols over to vinegar.

Be certain though that acetobacter never travels alone. It is most certainly more than one infection.

Acetobacter is aerobic so it can't live once you purge the o2 with co2. So if you want to try and rescue the beer the sooner the better. Not that I would, I'd dump it.

I know it is hard to tell from the picture, but it isn't fuzzy like mold, it was more like a plasticine film that had some bubbles in it. It didn't smell like vinegar, just like dark beer.

Acetobactor likes to form a plastic like film over the surface of the beer. The picture doesn't show that. However, if it the beer is taking on an acetic aroma and has a vinegar-like flavor then it is an acetobactor infection for sure.

It takes a while for the beer to start smelling like vinegar though. I've had acetobacter infections that actually didn't taste terrible. No sourness noted. Not something I could ever enjoy, but not much sourness going on either. It takes along time for acetobacter to fully convert the alcohols over to vinegar.

Be certain though that acetobacter never travels alone. It is most certainly more than one infection.

Acetobacter is aerobic so it can't live once you purge the o2 with co2. So if you want to try and rescue the beer the sooner the better. Not that I would, I'd dump it.

Agreed...it could be more than just one bug. Bottom line...if it tastes bad...it's a a dumper.